1. Field of the Invention
The present invention relates to the field of cable unwinders and rewinders, and more particularly to unwinders and rewinders having a dual reel configuration that provide a continuous electrical connection.
2. Related Art
The Government of the United States of America requires validation of pharmaceutical manufacturing facilities and that such facilities adhere to current good manufacturing practices (see, The Food, Drug and Cosmetic Act and Part 21 of the Code of Federal Regulations.) Besides the Government of the United States of America, governments of the European Union and other parts of the world impose similar requirements for the validation of pharmaceutical manufacturing facilities. There are companies such as PRFC, Inc., (Reno, Nev.) that assist pharmaceutical manufacturers with this validation.
The requirements for validation includes validating the efficacy of autoclaves. An autoclave is a sterilizer that has a heated chamber. In a typical set-up to validate an autoclave, a plurality of heat sensors, known as thermocouples, are positioned at various locations within the chamber of the autoclave. There is usually between about 15 to about 25 thermocouples that are positioned within the autoclave.
Each of these thermocouples that are positioned within the autoclave is connected via a separate thermocouple wire to a data logger/recorder. Normally, the thermocouple wire that is used is a heavy gauge cable. It has iron and copper strands which are encapsulated in insulation. The cable is approximately about 8 to about 12 gauge for a wire pair. Its physical properties are qualitatively described as thick, resilient and unruly. The data logger/recorder may be located up to 25 feet from the autoclave.
Thus, when validating an autoclave, there are about 15 to about 25 long thermocouple wires running between the autoclave and data logger/recorder that are unruly and untidy. The thermocouple wires often become entangled, twisted and disorganized. This can damage the thermocouple wire and make it difficult to position and disengage the data logger/recorder from the autoclave. Further, it is difficult to trace a thermocouple wire from the interconnected between the data logger/recorder to the autoclave. Being able to trace is critical to properly placing the wire and thermocouple in the autoclave chamber.
There is an art that teaches the design of unwinders/rewinders. One genre of unwinders/rewinders is for wires that provide power to alternating current devices such as such as power tools. These unwinders/rewinders employ brushes or slip rings to make a discontinuous electrical connection. Brushes and slip rings are suitable for providing alternating current for power tools; but, the discontinues nature of the connection is a source of undesirable electrical noise in the context of analytical equipment; e.g., voltage and current bounces and spikes.
Another genre of unwinders/rewinders employ mercury contacts for a continuous electrical connection. Mercury contacts are suitable for audio connections and test equipment in a non-food and non-drug environment. For obvious reasons, a toxic substance like mercury is undesirable and/or not suitable in the food and drug environment.
Another genre of unwinders/rewinders employ a dual reel system for continuous electrical connection. One such device is described in U.S. Pat. No. 1,276,825, issued on Aug. 27, 1918, to D. Swope, and incorporated herein by reference. The patent teaches dual reels disposed on axle within a housing. One of the reels is a user-side reel and the other reel is a slack-side reel. The slack-side reel has an inside diameter less than the inside diameter of the user-side reel. A loaded coil spring is superimposed on the reel axle to provide a rewind force. As cable is wound from the user-side reel, cable is simultaneously unwound unto a slack-side reel. The relatively smaller inside diameter of the slack-side reel results in a shorter length of cable winding/unwinding on the slack-side reel than that being unwound/wound on the user side reel.
This device has the drawback that the cable being unwound on the slack-side reel has nowhere to go but to pile up in a housing. Accordingly, the cable is subject to tangling, twisting, knotting and kinking, all of which impede the operation of the unwinder/rewinder. Further, if the device were fitted with heavy gauge cable, the heavy gauge cable which is stiff would resist piling up in the housing and thereby generate a back pressure retarding unwinding/winding. The device has the further drawback of insufficient force to rewind a heavy gauge cable, or in the alternative, requires a coil spring with such a great spring constant that unwinding requires cumbersome force and strains the mounting system.
U.S. Pat. No. 4,646,987, issued on Mar. 3, 1987 to E. Peterson, teaches a dual reel unwinder/rewinder for a telephone headset wire and is incorporated by reference. This device is designed for flat cable. A flat cable is thin tape that is soft, flexible and pliable. The device does not accommodate a heavy gauge cable which is relatively large, thick and stiff. The device has the disadvantage of utilizing two reels that are the same size which results in an equal length of flat cable unwinding on both reels during operation. Unwinding a equal length of cable on both sides wastes cable. The device has the additional disadvantage that the unwinder/rewinder travels as flat cable is wound and unwound. A still further disadvantage of this device is that the rewind mechanism is not strong enough to rewind heavy gauge cable, assuming the device could be fitted with heavy gauge cable.
Accordingly, there is a need for winder/unwinder that is suitable for use with scientific equipment (i.e., provides for an uninterrupted and continuous transmissions of a signal with low noise); suitable for use in the pharmaceutical manufacturing environment (e.g., does not contain toxic materials); accommodates heavy gauge cable; accommodates long lengths of cable; has an automatic rewind function; does not waste expensive cable; does not result in tangling, twisting, knotting and kinking of heavy gauge cable and remains stationary during operation.
The present invention satisfies these needs, as well as others, and generally overcomes the presently known deficiencies in the art.